Effects Of High Temperature Stress On Reproductive Organ Development And Yield Of Summer Maize

In recent years,Summer Maize had a short period of abnormal high temperature during anthesis and pollination in Hebei plain,which resulted in ear dysplasia and yield reduction.It was important to clarify the reproductive organ development characteristics of different heat-sensitive varieties under high temperature stress.The experiment was conducted at xinji experimental station of Hebei Agricultural University in 2018 year.The cultivars with Nongda 372(ND372)and xianyu 335(XY335)were used as the test materials,and were treated with high temperature and field treatment.The high temperature treatment was carried out in the plastic greenhouse,and the treatment lasted from sixth leaves to silking stage,with eight hours at each day.Relative temperature of 5 ± 0.5℃ were higher than that in the field.The response differences to high temperature stress were studied from the agronomic traits of tassel,pollen filament vigor and female tassel grain development in two maize cultivars,and futher transcriptome analysis in XY335,a heat-sensitive cultivars.This study can provide reference for high temperature tolerance and directional breeding in summer maize.The main results showed that:(1)The tassel size,volume and dry weight of maize decreased after high temperature treatment.The numbers of floret of main spike and branch decreased and the density of floret per unit area increased.The tassel size,volume and dry weights of ND372 decreased than that in XY335,the numbers of branched florets of ND372 and XY335 and the density of main spikelet decreased 30%,91%,19.3% and 250%,respectively.(2)The Anthesis-silking interval(ASI)period of maize increased after high temperature treatment,resultedin blocked powder dispersal,decreased powder quantity,accelerated powder dispersal rate,and decreased vitality of pollen and filaments.ND372 and XY335 increased 60% and 76.5%,respectively,pollen activity decreased 16% and 27%,respectively,and filament activity decreased 12.5% and 20.5%,respectively.(3)The epidermal cells in the anther wall of maize were deformed and loose in arrangement under high temperature treatment,and the middle cells were also deformed and loose in arrangement,the tapetal cells were degenerated,the vascular bundle cells were not orderly in arrangement,the vascular bundle became thinner,the pollen grains in the anther were scattered and the pollen shrived.The interstitial space of the pollen surface increases and thickens,forming severe folds.XY335 was more seriously affected by high temperature than that in ND372.(4)The effective panicle grain number per plant of ND372 was more than that of ungrouted grains after high temperature treatment,while the effective panicle grain number per plant of XY335 was the same as that of ungrouted grains per plant.In high temperature stress,the main ear deformity of ND372 were banana ear and grain deficiency,while the ear deformity of XY335 was grain non-filling.The yield of ND372 and XY335 decreased 70.8% and 232%,respectively.(5)XY335 showed significant differences in transcription level after high-temperature treatment.1222 differentially expressed genes were found by transcriptional sequencing technology,among which 586 differentially expressed genes were up-regulated and 636 differentially expressed genes were down-regulated.By comparing the differentially expressed genes with the database,a total of 1,185 differentially expressed genes were found,among which 489 differentially expressed genes were annotated in the COG database,952 differentially expressed genes were annotated in the GO database,443 differentially expressed genes were annotated in the KEGG database,623 differentially expressed genes were annotated in the KOG database,and 1,177 differentially expressed genes were annotated in the NR database.Based on the study results,the main conclusions could be concluded,The heat-resistance of ND372 was higher than that of XY335,and the tassel and ear ear development of heat-sensitive maize cultivars XY335 was more affected by high temperature stress than that of heat-resistant cultivars ND372.Transcriptome analysis on the anther(pollen)of heat sensitive maize cultivars XY335 showed that amino acid synthesis,carbohydrate metabolism and secondary substance metabolism played an important role in resisting response to high temperature stress.